1. Field of the Invention
The present invention relates to a fuel supply apparatus for pressurizing and supplying fuel to an injector which is attached within the fuel tank of an automobile etc. and injects fuel to an engine, and also relates to a residual fuel amount indication device for the fuel supply apparatus.
2. Related Art
Conventionally, there is known an apparatus shown in the International Publication No. WO96/23967 as a fuel supply apparatus for supplying fuel to an internal combustion engine and also there is known an apparatus shown in the Unexamined Japanese Patent Application Publication No. 2000-73900 as another fuel supply apparatus.
FIG. 3 shows the side sectional view of the conventional fuel supply apparatus shown in the Unexamined Japanese Patent Application Publication No.2000-73900, and FIG. 4 is the circuit diagram of the conventional residual fuel amount indication device shown in the Japanese Patent No. 2,860,846.
In FIG. 3, a reference numeral 1 depicts a fuel supply apparatus which is integrally configured by a lid 3, a fuel pump 4, a fuel filter 5, a fuel pressure adjuster 6, a discharge pipe 7, a fuel liquid level gauge 8, the float 9 of the fuel liquid level gauge 8, a housing casing 10 serving as a supporting member for housing and supporting the fuel pump 4, the fuel filter 5 and the fuel pressure adjuster 6, a strainer 11 for filtering fuel sucked into the fuel pump 4, and an electric connector 12. The fuel supply apparatus is suspended from the opening portion 2a of a fuel tank 2 formed by metal or resin.
The fuel filter 5 is configured by a filter casing 5a formed by resin molded parts and a filter element 5b housed therein. The fuel filter 5 and the fuel pump 4 are coupled to each other through a coupling pipe 13.
The fuel filter 5 and the discharge pipe 7 are coupled to each other through a coupling pipe 14. The fuel pressure adjuster 6 is disposed on the way of the coupling pipe 14 so as to adjust fuel supplied to the injector to a predetermined pressure.
The fuel liquid level gauge 8 and the float 9 constituting a fuel liquid level detection section is configured in a manner that the fuel liquid level gauge 8 is attached to the outer peripheral surface of the housing casing 10 and, when the float 9 moves vertically or elevationally in accordance with the liquid level of the fuel within the fuel tank 2, a resistance value changes in accordance with the liquid level. The resistance value is set to be small when the fuel amount is large and set to be large when the fuel amount is small. A signal representing the resistance value is outputted to the outside through the electric connector 12 disposed on the upper surface of the lid 3 from a lead wire 15.
The fuel pump 4 is electrically coupled to the electric connector 12 through a lead wire 16 and supplied with electric power from a battery mounted on a not-shown vehicle.
A reference numeral 17 depicts a gasket for holding airtightness disposed between the lid 3 and the fuel tank 2.
The operation of the fuel supply apparatus 1 configured in the aforesaid manner will be explained with reference to FIG. 3.
When electric power is supplied to the not-shown motor of the fuel pump 4 from the not-shown battery through the electric connector 12 and the lead wire 16, the motor rotates and so fuel within the fuel tank 2 is sucked (in a direction shown by an arrow A) within the fuel pump 4 through the strainer 11. Thereafter, the fuel thus sucked is pressurized to a predetermined pressure and then discharged (in a direction shown by an arrow B).
The fuel thus discharged passes through the coupling pipe 13 and the filter element 5b of the fuel filter 5, then flows into the fuel pressure adjuster 6 (in a direction shown by an arrow C) and also is supplied to the injector of the fuel injection apparatus attached to the not-shown engine through the coupling pipe 14 and the discharge pipe 7.
In this case, the adjustor 6 is arranged in a manner that when the fuel pressure within the coupling pipe 14 becomes higher than the predetermined pressure, the fuel within the coupling pipe 14 is discharged into the housing casing 10 (in a direction shown by an arrow D) and then returned into the fuel tank 2 through a not-shown fuel path, whereby the pressure of the fuel discharged from the discharge pipe 7 is adjusted to be less than the predetermined pressure.
Next, the operation of the residual fuel amount indication device 20 configured in the aforesaid manner will be explained with reference to FIG. 4.
The fuel liquid level gauge 8 is applied with the voltage +B of the battery through a resistor 21. As a result, an output voltage V1 in inverse proportion to a fuel amount within the fuel tank 2 is obtained from a connection point between the fuel liquid level gauge 8 and the resistor 21. The output voltage V1 of the fuel liquid level gauge 8 is inputted into a damper circuit 24 formed by a resistor 22 and a capacitor 23.
The damper circuit 24 is provided in order to prevent such a phenomenon that an indicator representing the fuel amount moves finely and so the indication value varies in a short time due to the vibration of the vehicle etc. caused when the vehicle runs. A time constant τ of the damper circuit 24 determined by the value of the resistor 22 and the value of the capacitor 23 is fixed to a constant value regardless of the fuel amount.
The output of the damper circuit 24 is amplified in its voltage by an amplifier 25, then amplified in its current by a transistor 26 and inputted to one excitation coil 27A of an excitation coil 27 for moving the indicator representing the fuel amount.
The excitation coil 27 is configured by the one excitation coil 27A and the other excitation coil 27B generating magnetic fluxes in different directions, respectively. The one excitation coil 27A is excited by the output current from the emitter of the transistor 26, whilst the other excitation coil 27B is always coupled to the voltage +B through a resistor 28 and so always excited by the constant current due to the voltage +B. In this case, the excitation coil 27A is arranged to generate such magnetic flux of displacing the indicator in the E side (small fuel amount side).
According to the residual fuel amount indication device 20 configured in the aforesaid manner, the output voltage of the fuel liquid level gauge 8 is integrated by the time constant τ in the damper circuit 24 thereby to absorb the short-time variation of the output voltage of the fuel liquid level gauge 8 caused by the vibration of the vehicle.
Thereafter, the output of the damper circuit is amplified by the amplifier 25 and the transistor 26 and then applied to the excitation coil 27A. Thus, the output voltage V1 of the fuel liquid level gauge 8 becomes larger as the residual fuel amount becomes smaller, and the excitation current of the excitation coil 27A becomes larger as the output voltage V1 of the fuel liquid level gauge 8 becomes larger and so the indicator representing the fuel amount is driven to the E side.
In contrast, when the fuel amount within the fuel tank 2 is large, the excitation current of the excitation coil 27A becomes small. Thus, the magnitude of the magnetic flux of the excitation coil 27A becomes small, so that the indicator representing the fuel amount is driven to the F side (full fuel amount side) due to the influence of the magnetic flux generated by the other excitation coil 27B.
In the case of suspending the fuel supply apparatus 1 configured in the aforesaid manner from the opening portion 2a of the fuel tank 2, since the fuel liquid level gauge 8 attached to the outer peripheral surface of the housing casing 10 and the float 9 engaged with the fuel liquid level gauge 8 protrude largely from the outer peripheral surface of the housing casing 10, there arises a problem that the fitting procedure is difficult.